The Blaugrana's back line is a cause for concern given their recent record and the need to overturn a two-goal deficit at home to the Italians in the Champions League on Tuesday

COMMENTBy Ben Hayward | Spanish Football Writer

More than 50 years have elapsed. The last time Barcelona conceded in 13 consecutive fixtures was way back in 1962, a bygone time when most of the club's current fans had not yet been born. So whatever the players and coaches may be saying, something is clearly amiss at the back - and it needs to be sorted out soon.

The long wait for a clean sheet has included three games against Malaga, three versus Real Madrid and one meeting with AC Milan, Getafe, Granada, Osasuna, Real Sociedad, Sevilla and Valencia apiece - 21 goals in total. And with their second-leg clash against Milan to come on Tuesday, the side's defensive difficulties represent a clear concern. Having lost 2-0 at San Siro, Barca claim to be confident of overcoming the Italians, yet concede just once and they will need to score four.

So where has it all gone wrong?

Part of the problem is a lack of leadership and guidance since coach Tito Vilanova travelled to New York for treatment in his fight against cancer (it is hoped he will return at the end of this month). In that time, though the whole team have dipped, the sector which has suffered the most has been the back line, which has shipped goals left, right and centre.

Defence for Barcelona begins in attack and with possession of the ball. And while the Catalans have continued to dominate in that department, their pressing from the front and in midfield has been less prominent in recent weeks, probably due in part to the side's intense pre-season campaign, which was geared towards getting off to a flying start in La Liga and the Spanish Supercopa. The latter was lost to Real Madrid over two close games, but Barca's league form in the early months gave them the healthy advantage they are currently enjoying over their fierce rivals in the Primera Division. Now, however, they are paying the price for their summer exertion as the season reaches its business end.

Fitness is one factor; form is another. At the beginning of the season, Barca were without injured pair Carles Puyol and Gerard Pique, forcing Vilanova to field players like Adriano, Alex Song, Sergio Busquets and even Thiago at the back. Defensive problems were understandable then, but not now. Puyol appears a shadow of his former self and struggled against both Milan and Madrid recently, while Pique appears to lack concentration and is clearly missing the motivation of former coach Pep Guardiola, let alone Tito. Dani Alves, meanwhile, has fallen into a sharp decline and is being targeted by teams looking to exploit his sector, while Jordi Alba's attacking down the left flank - coupled with the Brazilian's forays forward - leave the centre-backs exposed to quick breaks. Madrid, in particular, were able to exploit this to perfection in their two recent wins over the Catalans.

When Eric Abidal, still on the long road back from his liver transplant, played at left-back for Barca, he would slot in as third central defender as Alves attacked - which was most of the time. That is not happening now and although Alba has been impressive, the lack of balance at the back is hurting Tito's team.

Abidal, at 1.86m, was also one of Barcelona's tallest players and his muscular physique and aerial ability proved useful to what is the smallest side in Europe's elite competitions in terms of average squad height. Alba, for all his qualities, is some 16 centimetres shorter than the Frenchman and Barca are perhaps more vulnerable now than before on set pieces. Adriano, and previously Maxwell, are also small in stature, yet Guardiola's Barca appeared to cope better in the absence of Abidal, with Puyol and Pîque an almost impregnable pairing at their best, with Javier Mascherano deputising with aplomb. But the Argentine, like his team-mates, has dipped in form this term and the whole side have lost their defensive stability over the last couple of months. Even goalkeeper Victor Valdes, suspended for four league matches after insulting referee Miguel Angel Perez Lasa following the Clasico last weekend, has been below his best in 2012-13.

Holding midfielder Busquets still drops deep to help out his team-mates, but Barca are often a man short as their full-backs attack and Vilanova - in consultation with interim coach Jordi Roura - needs to find a solution fast. And he needs his players back on form for Tuesday's crunch clash.

Barca host bottom club Deportivo La Coruna at Camp Nou before that on Saturday in what would appear the ideal opportunity to keep a clean sheet and boost morale ahead of the Milan match on Tuesday, because if they concede against the Italians, the Catalans will need to score four times to advance to the last eight of the Champions League. And on current form, that looks like a tall order.